scholarly journals Role of Macrocyclic Conformational Steering in a Kinetic Route toward Bielschowskysin

2020 ◽  
Author(s):  
Paul Scesa ◽  
Lyndon M. West ◽  
Stephane Roche
Keyword(s):  
Natural Products ◽  
Selective Oxidation ◽  
Synthetic Methods ◽  
Kinetic Control ◽  
Kinetically Controlled ◽  
Conformational Preferences ◽  
Stereoselective Epoxidation ◽  
Site Selective

Macrocyclic furanobutenolide-derived cembranoids (FBCs) are the biosynthetic precursors to a wide variety of highly congested and oxygenated polycyclic (nor)diterpenes (<i>e.g.</i> plumarellide, verrillin or bielschowskysin). These architecturally complex metabolites are thought to originate from site-selective oxidation of the macrocycles’ backbone and a series of intricate transannular reactions. Yet the development of a common biomimetic route has been hampered by a lack of synthetic methods for the pivotal furan dearomatization in a regio- and stereoselective manner. To address these shortcomings, a concise strategy of chemo- and stereoselective epoxidation followed by a kinetically-controlled furan dearomatization is reported. The surprising switch of facial <i>a</i>:<i>b</i>-discrimination observed in the epoxidations of the most strained <i>E</i>-acerosolide <i>versus</i> <i>E</i>-deoxypukalide and <i>E</i>-bipinnatin J derived macrocycles has been rationalized by the 3D-conformational preferences of the macrocyclic scaffolds. The downstream functionalization of FBC-macrocycles was also studied, and how the C-7 epoxide configuration was retentively translated to the C-3 stereogenicity in dearomatized products under kinetic control to secure the requisite (3<i>S</i>,7<i>S</i>,8<i>S</i>)-configurations for the bielschowskysin synthesis. Unlike previously speculated, our results suggest that the most strained FBC-macrocycles bearing a <i>E</i>-(D<sup>7,8</sup>)-alkene moiety may stand as the true biosynthetic precursors to bielschowskysin and several other polycyclic natural products of this class.

Role of Macrocyclic Conformational Steering in a Kinetic Route toward Bielschowskysin

2020 ◽  
Author(s):  
Paul Scesa ◽  
Lyndon M. West ◽  
Stephane Roche
Keyword(s):  
Natural Products ◽  
Selective Oxidation ◽  
Synthetic Methods ◽  
Kinetic Control ◽  
Kinetically Controlled ◽  
Conformational Preferences ◽  
Stereoselective Epoxidation ◽  
Site Selective

Macrocyclic furanobutenolide-derived cembranoids (FBCs) are the biosynthetic precursors to a wide variety of highly congested and oxygenated polycyclic (nor)diterpenes (<i>e.g.</i> plumarellide, verrillin or bielschowskysin). These architecturally complex metabolites are thought to originate from site-selective oxidation of the macrocycles’ backbone and a series of intricate transannular reactions. Yet the development of a common biomimetic route has been hampered by a lack of synthetic methods for the pivotal furan dearomatization in a regio- and stereoselective manner. To address these shortcomings, a concise strategy of chemo- and stereoselective epoxidation followed by a kinetically-controlled furan dearomatization is reported. The surprising switch of facial <i>a</i>:<i>b</i>-discrimination observed in the epoxidations of the most strained <i>E</i>-acerosolide <i>versus</i> <i>E</i>-deoxypukalide and <i>E</i>-bipinnatin J derived macrocycles has been rationalized by the 3D-conformational preferences of the macrocyclic scaffolds. The downstream functionalization of FBC-macrocycles was also studied, and how the C-7 epoxide configuration was retentively translated to the C-3 stereogenicity in dearomatized products under kinetic control to secure the requisite (3<i>S</i>,7<i>S</i>,8<i>S</i>)-configurations for the bielschowskysin synthesis. Unlike previously speculated, our results suggest that the most strained FBC-macrocycles bearing a <i>E</i>-(D<sup>7,8</sup>)-alkene moiety may stand as the true biosynthetic precursors to bielschowskysin and several other polycyclic natural products of this class.

scholarly journals Regioselective Functionalization of Quinolines through C-H Activation: A Comprehensive Review

Molecules ◽  
2021 ◽  
Vol 26 (18) ◽  
pp. 5467
Author(s):  
Alessandra Corio ◽  
Christine Gravier-Pelletier ◽  
Patricia Busca
Keyword(s):  
Natural Products ◽  
Transition Metal ◽  
Green Chemistry ◽  
Transition Metal Catalysis ◽  
Synthetic Methods ◽  
Metal Catalysis ◽  
Comprehensive Review ◽  
Metal Catalyzed ◽  
Regioselective Functionalization ◽  
Site Selective

Quinoline is a versatile heterocycle that is part of numerous natural products and countless drugs. During the last decades, this scaffold also became widely used as ligand in organometallic catalysis. Therefore, access to functionalized quinolines is of great importance and continuous efforts have been made to develop efficient and regioselective synthetic methods. In this regard, C-H functionalization through transition metal catalysis, which is nowadays the Graal of organic green chemistry, represents the most attractive strategy. We aim herein at providing a comprehensive review of methods that allow site-selective metal-catalyzed C-H functionalization of quinolines, or their quinoline N-oxides counterparts, with a specific focus on their scope and limitations, as well as mechanistic aspects if that accounts for the selectivity.

Pharmacologic Role of Vitamin D Natural Products

2014 ◽  
Vol 12 (2) ◽  
pp. 278-285 ◽  
Author(s):  
Pablo Urena-Torres ◽  
Jean Souberbielle
Keyword(s):  
Vitamin D ◽  
Natural Products

Application of Dess-Martin oxidation in total synthesis of natural products

2020 ◽  
Vol 17 ◽  
Author(s):  
Majid M. Heravi ◽  
Tayebe Momeni ◽  
Vahideh Zadsirjan ◽  
Leila Mohammadi
Keyword(s):  
Natural Products ◽  
Total Synthesis ◽  
Selective Oxidation ◽  
Secondary Alcohols ◽  
Aldehydes And Ketones

: Dess–Martin periodinane (DMP), is a commercially available chemical, frequently being utilized as a mild oxidative agent for the selective oxidation of primary and secondary alcohols to their corresponding aldehydes and ketones, respectively. DMP shows several merits over other common oxidative agent such as chromium- and DMSO-based oxidants, thus it is habitually employed in the total synthesis of natural products. In this review, we try to underscore the applications of DMP as an effective oxidant in an appropriate step (steps) in the multistep total synthesis of natural products.

Role of Zeolites and Zeotypes in Green Chemistry

2020 ◽  
Vol 07 ◽  
Author(s):  
Jyotsna S. Meshram ◽  
Devendra S. Raghuvanshi
Keyword(s):  
Green Chemistry ◽  
Industrial Process ◽  
Environmental Issues ◽  
Synthetic Methods ◽  
Acid Catalysts ◽  
Chemical Waste ◽  
Specific Morphology

Abstract:: Now days, it is of utmost important to design synthetic methods; which can be utilized for the generation of substances that will minimize toxicity to health of human and the environment. The utilization of acid catalysts generates lots of corrosive and harmful wastes which has to be treated with appropriate alkalis. Hence, it generates lots of sludge and alarms environmental issues of its storage and disposal. Zeolites and Zeotypes; by virtue of their peculiar properties; such as specific morphology, porosity and residing acidity; attracting enormous attention as they replaces harmful acid catalysts efficiently and also reduces chemical waste in industrial process; Hence emerged as new plethora in the field of “Green Chemistry”.

scholarly journals Rational Generation of Lasso Peptides Based on Biosynthetic Gene Mutations and Site-Selective Chemical Modifications

2021 ◽  
Author(s):  
Tan Liu ◽  
Xiaojie Ma ◽  
Jiahui Yu ◽  
Wensheng Yang ◽  
guiyang wang ◽  
...  
Keyword(s):  
Natural Products ◽  
Gene Mutations ◽  
Proteolytic Degradation ◽  
Biosynthetic Gene ◽  
Chemical Modifications ◽  
Lasso Peptides ◽  
Selective Chemical ◽  
Site Selective

Lasso peptides are a unique family of natural products whose structures feature a specific threaded fold, which confers these peptides the resistance to thermal and proteolytic degradation. This stability gives...

scholarly journals Oxidation of Terpenoids to Achieve High-Value Flavor and Fragrances—Questioning Microalgae Oxidative Capabilities in the Biotransformation of the Sesquiterpene Valencene and of Selected Natural Apocarotenoids

Chemistry ◽  
2021 ◽  
Vol 3 (3) ◽  
pp. 821-830
Author(s):  
Davide De Simeis ◽  
Stefano Serra ◽  
Alessandro Di Fonzo ◽  
Francesco Secundo
Keyword(s):  
Experimental Data ◽  
Natural Products ◽  
Aqueous Medium ◽  
Photochemical Reaction ◽  
Substrate Oxidation ◽  
Market Size ◽  
Chlorella Sp ◽  
General Opinion ◽  
Natural Way

Natural flavor and fragrance market size is expected to grow steadily due to the rising consumer demand of natural ingredients. This market request is guided by the general opinion that the production of natural compounds leads to a reduction of pollution, with inherent advantages for the environment and people’s health. The biotransformation reactions have gained high relevance in the production of natural products. In this context, few pieces of research have described the role of microalgae in the oxidation of terpenoids. In this present study, we questioned the role of microalgal based oxidation in the synthesis of high-value flavors and fragrances. This study investigated the role of three different microalgae strains, Chlorella sp. (211.8b and 211.8p) and Chlorococcum sp. (JB3), in the oxidation of different terpenoid substrates: α-ionone, β-ionone, theaspirane and valencene. Unfortunately, the experimental data showed that the microalgal strains used are not responsible for the substrate oxidation. In fact, our experiments demonstrate that the transformation of the four starting compounds is a photochemical reaction that involves the oxygen as oxidant. Even though these findings cast a shadow on the use of these microorganisms for an industrial purpose, they open a new possible strategy to easily obtain nootkatone in a natural way by just using an aqueous medium, oxygen and light.

scholarly journals Modern Synthetic Methods for the Stereoselective Construction of 1,3-Dienes

Molecules ◽  
2021 ◽  
Vol 26 (2) ◽  
pp. 249
Author(s):  
Raquel G. Soengas ◽  
Humberto Rodríguez-Solla
Keyword(s):  
Organic Chemistry ◽  
Natural Products ◽  
Functional Group ◽  
Biological Activities ◽  
Synthetic Methods ◽  
Bond Forming ◽  
Drug Candidates ◽  
The Past ◽  
Wide Range

The 1,3-butadiene motif is widely found in many natural products and drug candidates with relevant biological activities. Moreover, dienes are important targets for synthetic chemists, due to their ability to give access to a wide range of functional group transformations, including a broad range of C-C bond-forming processes. Therefore, the stereoselective preparation of dienes have attracted much attention over the past decades, and the search for new synthetic protocols continues unabated. The aim of this review is to give an overview of the diverse methodologies that have emerged in the last decade, with a focus on the synthetic processes that meet the requirements of efficiency and sustainability of modern organic chemistry.

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